LT1505
Constant-Current/Voltage
High Efficiency Battery Charger
DESCRIPTIO
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FEATURES
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The LT®1505 PWM battery charger controller fast charges
multiple battery chemistries including lithium-ion (Li-Ion),
nickel-metal-hydride (NiMH) and nickel-cadmium (NiCd)
using constant-current or constant-voltage control. Maximum current can be easily programmed by resistors or a
DAC. The constant-voltage output can be selected for 3 or 4
series Li-Ion cells with 0.5% accuracy.
Simple Charging of Li-Ion, NiMH and NiCd Batteries
Very High Efficiency: Up to 97%
Precision 0.5% Charging Voltage Accuracy
Preset Battery Voltages: 12.3V, 12.6V,
16.4V and 16.8V
5% Charging Current Accuracy
Charging Current Programmed by Resistor or DAC
0.5V Dropout Voltage, Duty Cycle > 99.5%
AC Adapter Current Limit* Maximizes Charging Rate
Flag Indicates Li-Ion Charge Completion
Auto Shutdown with Adapter Removal
Only 10µA Battery Drain When Idle
Synchronizable Up to 280kHz
A third control loop limits the current drawn from the AC
adapter during charging*. This allows simultaneous operation of the equipment and fast battery charging without overloading the AC adapter.
The LT1505 can charge batteries ranging from 2.5V to 20V
with dropout voltage as low as 0.5V. Synchronous
N-channel FETs switching at 200kHz give high efficiency
and allow small inductor size. A diode is not required in
series with the battery because the charger automatically
enters a 10µA sleep mode when the wall adapter is unplugged. A logic output indicates Li-Ion full charge when
current drops to 20% of the programmed value.
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APPLICATIO S
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Notebook Computers
Portable Instruments
Chargers for Li-Ion, NiMH, NiCd and Lead Acid
Rechargeable Batteries
The LT1505 is available in a 28-pin SSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
*US Patent No. 5,723,970
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TYPICAL APPLICATION
TO
SYSTEM POWER
M3
Si4435
DBODY*
VIN
(FROM
ADAPTER)
C4
0.1µF
RS4
0.025Ω
R7
500Ω
C1
1µF
CIN
47µF
35V
100k
R5
4k
VCC
BOOST
BOOSTC
GBIAS
CLN
CLP
TGATE
INFET
BGATE
SW
SYNC
*BODY DIODE
POLARITY MUST
BE AS SHOWN
LT1505
3 CELL
FLAG
VFB
CAP
4.2V
4.1V
R1
1k
C7
0.68µF
AGND
PGND
BAT2 BAT
L1
15µH
M1
Si4412
5Ω
RS1
0.025Ω
VBAT
M2
Si4412
COUT
22µF
25V
×2
D4
MBRS140
SENSE
12.6V
BATTERY
PROG
SHDN
COMP1
C6
0.1µF
C2
0.68µF
C3
D2
2.2µF MMSD4148T1
VC
UV
R6
4k
D3
MMSD4148T1
SPIN
300Ω
CPROG
1µF
RPROG
4.93k
1%
RX4
3k
0.33µF
RS2
200Ω
1%
RS3
200Ω
1%
* DBODY IS THE BODY DIODE OF M3
CIN: SANYO OS-CON
L1: SUMIDA CDRH127-150
(CAN BE FROM 10µH TO 30µH)
1505 F01
Figure 1. Low Dropout 4A Lithium-Ion Battery Charger
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LT1505
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ABSOLUTE MAXIMUM RATINGS (Note 1)
VCC, CLP, CLN, INFET, UV, 3CELL, FLAG................ 27V
SW Voltage with Respect to GND ........................... – 2V
BOOST, BOOSTC Voltage with Respect to VCC ....... 10V
GBIAS ..................................................................... 10V
SYNC, BAT2, BAT, SENSE, SPIN ............................ 20V
VC, PROG, VFB, 4.1V, 4.2V ........................................ 7V
CAP, SHDN .......................................................... ±3mA
TGATE, BGATE Current Continuous ....................... 0.2A
TGATE, BGATE Output Energy (per cycle) ............... 2µJ
Maximum Operating VCC ......................................... 24V
Operating Ambient Temperature Range ....... 0°C to 70°C
Operating Junction Temperature Range .... 0°C to 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
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PACKAGE/ORDER INFORMATION
TOP VIEW
BOOST
1
28 PGND
TGATE
2
27 BGATE
SW
3
26 GBIAS
SYNC
4
SHDN
AGND
ORDER PART
NUMBER
1
28 PGND
TGATE
2
27 BGATE
SW
3
26 GBIAS
25 BOOSTC
SYNC
4
25 BOOSTC
5
24 VCC
SHDN
5
24 VCC
6
23 BAT
AGND
6
23 BAT
UV
7
22 SPIN
UV
7
22 SPIN
INFET
8
21 SENSE
INFET
8
21 SENSE
CLP
9
20 BAT2
NC
9
20 BAT2
CLN 10
19 PROG
NC 10
19 PROG
COMP1 11
CAP 12
FLAG 13
4.1V 14
LT1505CG
18 VC
GND 11
18 VC
17 VFB
CAP 12
17 VFB
16 3CELL
FLAG 13
15 4.2V
4.1V 14
G PACKAGE
28-LEAD PLASTIC SSOP
LT1505CG-1
16 3CELL
15 4.2V
G PACKAGE
28-LEAD PLASTIC SSOP
TJMAX = 125°C, θJA = 100°C/ W
ORDER PART
NUMBER
TOP VIEW
BOOST
NOTE: LT1505CG-1 DOES NOT
HAVE INPUT CURRENT
LIMITING FUNCTION.
TJMAX = 125°C, θJA = 100°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 18V, VBAT = 12.6V, VCLN = VCC (LT1505), no load on any
outputs unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
12
15
mA
100
10
105
108
13
mV
mV
mV
VBOOST = VSW + 8V, 0V ≤ VSW ≤ 20V
TGATE High
TGATE Low
2
2
3
3
mA
mA
VBOOSTC = VCC + 8V
1
Overall
Supply Current
VCC ≤ 24V
Sense Amplifier CA1 Gain and Input Offset Voltage
(With RS2 = 200Ω, RS3 = 200Ω)
(Measured across RS1, Figure 1) (Note 2)
11V ≤ VCC ≤ 24V , 0V ≤ VBAT ≤ 20V
RPROG = 4.93k
RPROG = 4.93k
RPROG = 49.3k
BOOST Pin Current
BOOSTC Pin Current
●
●
95
92
7
mA
Reference
Reference Voltage (Note 3)
RPROG = 4.93k, Measured at VFB with VA
Supplying IPROG and Switching Off
Reference Voltage Tolerance
11V ≤ VCC ≤ 24V
2.453
●
2.441
2.465
2.477
2.489
V
V
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LT1505
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 18V, VBAT = 12.6V, VCLN = VCC (LT1505), no load on any
outputs unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Preset Battery Voltage (12.3V, 16.4V, 12.6V, 16.8V)
All Preset Battery Voltages
Measured at BAT2 Pin
Preset Battery Voltage Tolerance
(VBAT + 0.3V) ≤ VCC ≤ 24V
●
0.5
BAT2 Pin Input Current
VBAT2 = VPRESET – 1V
●
Voltage Setting Resistors Tolerance (R4, R5, R6, R7)
–1
%
1
%
6
µA
40
%
7.25
V
5
µA
50
µA
2
V
8
µA
15
20
mA
–1
–4
– 22
µA
–1
– 2.4
– 40
Shutdown
Undervoltage Lockout (TGATE and BGATE “Off”)
Threshold (Note 9)
Measured at UV Pin
●
6.3
UV Pin Input Current
0V ≤ VUV ≤ 8V
●
–1
Reverse Current from Battery in Micropower
Shutdown (Note 10)
VBAT ≤ 20V, VUV ≤ 0.4V,
VCC = VSW = Battery Voltage
Shutdown Threshold at SHDN Pin When VCC
is Connected
10
●
SHDN Pin Current
0V ≤ VSHDN ≤ 3V
Supply Current in Shutdown
(VSHDN is Low, VCC is Connected)
VCC ≤ 24V
Minimum IPROG for Switching “On”
Minimum IPROG for Switching “Off” at VPROG ≤ 1V
6.7
●
1
mA
Current Sense Amplifier CA1 Inputs (SENSE, BAT)
Input Bias Current (SENSE, BAT)
VSHDN = High
VSHDN = Low (Shutdown)
– 50
●
– 120
– 10
Input Common Mode Low
●
Input Common Mode High
●
VCC – 0.3
●
2
10
mA
µA
SPIN Input Current
VSHDN = High, VSPIN ≥ 2V (Note 8)
VSHDN = Low (Shutdown)
– 0.25
µA
µA
V
V
Oscillator
Switching Frequency (fNOM)
Switching Frequency Tolerance
SYNC Pin Input Current
●
180
200
220
kHz
170
200
230
kHz
– 0.5
– 30
mA
µA
2.0
V
280
kHz
7.6
V
V
VSYNC = 0V
VSYNC = 2V
Synchronization Pulse Threshold on SYNC Pin
0.9
Synchronization Frequency
1.2
●
240
●
6.8
7.3
0.25
●
85
90
150
200
Maximum Duty Cycle
VBOOST Threshold to Turn TGATE Off
(Comparator A2) (Note 4)
Measured at (VBOOST – VSW)
Low to High
Hysteresis
Maximum Duty Cycle of Natural Frequency 200kHz
(Note 5)
%
Current Amplifier CA2
Transconductance
VC = 1V, IVC = ±1µA
Maximum VC for Switch Off
300
µmho
●
0.6
V
µA
mA
IVC Current (Out of Pin)
VC ≥ 0.6V
VC < 0.45V
●
●
50
3
VC at Shutdown
VSHDN = Low (Shutdown)
●
0.35
V
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LT1505
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 18V, VBAT = 12.6V, VCLN = VCC (LT1505), no load on any
outputs unless otherwise noted.
PARAMETER
Voltage Amplifier VA
Transconductance (Note 3)
CONDITIONS
MIN
TYP
MAX
UNITS
0.6
1.0
mho
25
mA
nA
Output Current from 50µA to 500µA
0.21
VFB = VPROG = VREF + 10mV
At 0.5mA VA Output Current, TA < 70°C
(3 CELL, 4.1V, 4.2V Are Not Connected, VBAT2 = 0V)
1.1
– 10
Turn-On Threshold
Transconductance
0.5mA Output Current
Output Current from 50µA to 500µA
87
0.5
CLP Input Current
CLN Input Current
0.5mA Output Current
0.5mA Output Current
Input P-Channel FET Driver (INFET)
INFET “On” Clamping Voltage (VCC – VINFET)
VCC ≥ 11V
●
INFET “On” Driver Current
INFET “Off” Clamping Voltage (VCC – VINFET)
VINFET = VCC – 6V
VCC Not Connected, IINFET < – 2µA
●
INFET “Off” Drive Current
Charging Completion Flag (Comparator E6)
VCC Not Connected, (VCC – VINFET) ≥ 2V
Charging Completion Threshold (Note 6)
Threshold On CAP Pin
VCAP at Shutdown
Measured at VRS1, VCAP = 2V (Note 7)
Low to High Threshold
High to Low Threshold
VSHDN = Low (Shutdown)
FLAG (Open Collector) Output Low
FLAG Pin Leakage Current
VCAP = 4V, I FLAG < 1mA
VCAP = 0.6V
●
●
●
8.4
VTGATE High (VTGATE – VSW)
11V < VCC < 24V, IGBIAS ≤ 15mA
VSHDN = Low (Shutdown)
ITGATE ≤ 20mA, VBOOST = VGBIAS – 0.5V
●
5.6
9.1
1
6.6
VBGATE High
VTGATE Low (VTGATE – VSW)
IBGATE ≤ 20mA
ITGATE ≤ 50mA
●
6.2
7.2
VBGATE Low
Peak Gate Drive Current
IBGATE ≤ 50mA
10nF Load
●
Gate Drive Rise and Fall Time
VTGATE, VBGATE at Shutdown
1nF Load
VSHDN = Low (Shutdown)
ITGATE = IBGATE = 10µA
Output Source Current
VFB Input Bias Current
Current Limit Amplifier CL1
Gate Drivers (TGATE, BGATE)
VGBIAS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Tested with Test Circuit 1.
Note 3: Tested with Test Circuit 2.
Note 4: When VCC and battery voltage differential is low, high duty factor
is required. The LT1505 achieves a duty factor greater than 99% by
skipping cycles. Only when VBOOST drops below the comparator A2
threshold will TGATE be turned off. See Applications Information.
Note 5: When the system starts, C2 (boost cap) has to be charged up to
drive TGATE and to start the system. The LT1505 will keep TGATE off and
turn BGATE on for 0.2µs at 200kHz to charge up C2. Comparator A2
senses VBOOST and switches to the normal PWM mode when VBOOST is
above the threshold.
92
1
97
3
mV
mho
1
0.8
3
2
µA
mA
6.5
7.8
9
8
20
1.4
– 2.5
14
●
●
20
3.3
mA
28
4.2
0.3
mV
V
V
V
0.3
3
V
µA
9.6
3
V
V
V
0.6
0.13
●
●
0.8
●
0.8
1
25
●
V
mA
V
1
V
V
V
A
ns
V
Note 6: See “Lithium-Ion Charging Completion” in the Applications
Information Section.
Note 7: Tested with Test Circuit 3.
Note 8: ISPIN keeps switching on to keep VBAT regulated when battery is
not present to avoid high surge current from COUT when battery is
inserted.
Note 9: Above undervoltage threshold switching is enabled.
Note 10: Do not connect VCC directly to VIN (see Figure 1). This connection
will cause the internal diode between VBAT and VCC to be forward-biased
and may cause high current to flow from VIN. When the adapter is
removed, VCC will be held up by the body diode of M1.
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LT1505
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TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency of Figure 1 Circuit
VGBIAS vs IGBIAS
105
VIN = 19V
VBAT = 12.6V
0.003
0°C
9.1
100
0°C ≤ TJ ≤ 125°C
25°C
0.002
9.0
125°C
8.9
90
0.001
8.8
∆VREF (V)
95
VGBIAS (V)
EFFICIENCY (%)
VREF Line Regulation
9.2
8.7
8.6
0
–0.001
8.5
85
ALL TEMPERATURES
8.4
–0.002
8.3
80
–0.003
8.1
0
1
3
2
4
5
0
IBAT (A)
–2 –4 –6 –8 –10 –12 –14 –16 –18 –20
IGBIAS (mA)
1505 G01
4
15
96
14
94
13
ICC (mA)
THRESHOLD (mV)
∆VFB (mV)
1
92
90
12
25
30
0°C
25°C
11
25°C
125°C
88
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
IVA (mA)
0
25
50
75
100
TEMPERATURE (°C)
10
125
10
13
16
19
VCC (V)
22
25
1505 G05
1505 G04
PROG Pin Characteristics
1505 G06
VC Pin Characteristics
Reference Voltage vs Temperature
2.470
–1.2
CURRENT FEEDBACK
AMPLIFIER OPEN LOOP
–1.0
2.468
REFERENCE VOLTAGE (V)
–0.8
–0.6
125°C
–0.4
IVC (mA)
IPROG (mA)
20
ICC vs VCC
98
3
6
15
VCC (V)
1505 G03
Current Limit Amplifier
CL1 Threshold
125°C
10
5
1505 G02
∆VFB vs IVA (Voltage Amplifier)
2
0
25°C
0
–0.2
0
0.2
0.4
0.6
2.466
2.464
2.462
2.460
0.8
–6
2.458
1.0
0
1
2
3
VPROG (V)
4
5
1505 G07
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
VC (V)
1505 G08
0
125
50
75
100
25
JUNCTION TEMPERATURE (°C)
150
1505 G09
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LT1505
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PIN FUNCTIONS
BOOST (Pin 1): This pin is used to bootstrap and supply
power for the topside power switch gate drive and control
circuity. In normal operation, VBOOST is powered from an
internally generated 8.6V regulator VGBIAS, VBOOST ≈ VCC
+ 9.1V when TGATE is high. Do not force an external
voltage on BOOST pin.
TGATE (Pin 2): This pin provides gate drive to the topside
power FET. When TGATE is driven on, the gate voltage will
be approximately equal to VSW + 6.6V. A series resistor of
5Ω to 10Ω should be used from this pin to the gate of the
topside FET.
SW (Pin 3): This pin is the reference point for the floating
topside gate drive circuitry. It is the common connection
for the top and bottom side switches and the output
inductor. This pin switches between ground and VCC with
very high dv/dt rates. Care needs to be taken in the PC
layout to keep this node from coupling to other sensitive
nodes. A 1A Schottky clamp diode should be placed from
this pin to the ground pin, using very short traces to
prevent the chip substrate diode from turning on. See
Applications Information for more details.
SYNC (Pin 4): Synchronization Input. The LT1505 can be
synchronized to an external clock with pulses that have
duty cycles between 10% and 95%. An internal one shot
that is triggered on the rising edge of the sync pulse makes
this input insensitive to the duty cycle of the sync pulse.
The input voltage range on this pin is 0V to 20V. This pin
can float if not used.
SHDN (Pin 5): Shutdown. When this pin is pulled below 1V,
switching will stop, GBIAS will go low and the input currents of CA1 will be off. Note that input current of about 4µA
keeps the device in shutdown unless an external pull-up
signal is applied. The voltage range on this pin is 0V to VCC.
AGND (Pin 6): Low Current Analog Ground.
UV (Pin 7): Undervoltage Lockout Input. The rising threshold is 6.7V with a hysteresis of 0.5V. Switching stops in
undervoltage lockout. When the input supply (normally
the wall adapter output) to the chip is removed, the UV pin
must be pulled down to below 0.7V (a 5k resistor from
adapter output to GND is required), otherwise the reversebattery current will be approximately 200µA instead of
10µA. Do not leave the UV pin floating. If it is connected
to VIN with no resistor divider, the built-in 6.7V undervoltage
lockout will be effective. Maximum voltage allowed on this
pin is VCC.
INFET (Pin 8): For very low dropout applications, an
external P-channel MOSFET can be used to connect the
input supply to VCC. This pin provides the gate drive for the
PFET. The gate drive is clamped to 8V below VCC. The gate
is driven on (low) when VCC > (VBAT + 0.2V) and
VUV > 6.7V. The gate is off (high) when VCC < (VBAT + 0.2V).
The body diode of the PFET is used to pull up VCC to turn
on the LT1505.
CLP (Pin 9): LT1505: Positive Input to the Input Current
Limit Amplifier CL1. The threshold is set at 92mV. When
used to limit input current, a filter is needed to filter out the
200kHz switching noise. (LT1505-1: No Connection.)
CLN (Pin 10): LT1505: Negative Input to the Input Current
Limit Amplifier CL1. When used, both CLP and CLN should
be connected to a voltage higher than 6V and normally
VCC (to the VCC bypass capacitor for less noise). Maximum
voltage allowed on both CLP and CLN is VCC + 1V.
(LT1505-1: No Connection.)
COMP1 (Pin 11): LT1505: Compensation Node for the
Input Current Limit Amplifier CL1. At input adapter current
limit, this pin rises to 1V. By forcing COMP1 low with an
external transistor, amplifier CL1 will be disabled (no
adapter current limit). Output current is less than 0.2mA.
See the Figure 1 circuit for the required resistor and
capacitor values. (LT1505-1: connect to GND.)
CAP (Pin 12): A 0.1µF capacitor from CAP to ground is
needed to filter the sampled charging current signal. This
filtered signal is used to set the FLAG pin when the
charging current drops below 20% of the programmed
maximum charging current.
FLAG (Pin 13): This pin is an open-collector output that is
used to indicate the end of charge. The FLAG pin is driven
low when the charge current drops below 20% of the
programmed charge current. A pull-up resistor is
required if this function is used. This pin is capable of
sinking at least 1mA. Maximum voltage on this pin is VCC.
4.1V (Pin 14), 4.2V (Pin 15), 3CELL (Pin 16), VFB (Pin
17): These four pins are used to select the battery voltage
using the preset internal resistor network. The VFB pin is
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LT1505
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PIN FUNCTIONS
the noninverting input to the amplifier, VA in the Block
Diagram, that controls the charging current when the
device operates in constant voltage mode. The amplifier
VA controls the charging current to maintain the voltage
on the VFB pin at the reference voltage (2.465V). Input bias
current for VA is approximately 3nA. The LT1505 incorporates a resistor divider that can be used to select the
correct voltage for either three or four 4.1V or 4.2V
lithium-ion cells. For three cells the 3CELL pin is shorted
to the VFB pin. For four cells the 3CELL pin is not connected. For 4.1V cells the 4.1V pin is connected to the VFB
pin and the 4.2V pin is not connected. For 4.2V cells the
4.2V pin is connected to VFB and the 4.1V pin is not
connected. See the table below.
PRESET BATTERY VOLTAGE
PIN SELECTION
12.3V (3 × 4.1V Cell)
4.1V, VFB, 3CELL Short Together
16.4V (4 × 4.1V Cell)
4.1V, VFB, Short Together, 3CELL Floats
12.6V (3 × 4.2V Cell)
4.2V, VFB, 3CELL Short Together
16.8V (4 × 4.2V Cell)
4.2V, VFB, Short Together, 3CELL Floats
For battery voltages other than the preset values, an
external resistor divider can be used. If an external divider
is used then the 4.1V, 4.2V and 3CELL pins should not be
connected and BAT2 pin should be grounded. To maintain
the tight voltage tolerance, the external resistors should
have better than 0.25% tolerance. Note that the VFB pin will
float high and inhibit switching if it is left open.
VC (Pin 18): This is the control signal of the inner loop of
the current mode PWM. Switching starts at 0.9V, higher
VC corresponds to higher charging current in normal
operation and reaches 1.1V at full charging current. A
capacitor of at least 0.33µF to GND filters out noise and
controls the rate of soft start. Pulling this pin low will stop
switching. Typical output current is 60µA.
PROG (Pin 19): This pin is for programming the charge
current and for system loop compensation. During normal
operation, VPROG stays at 2.465V. If it is shorted to GND or
more than 1mA is drawn out of the pin, switching will stop.
When a microprocessor controlled DAC is used to program charging current, it must be capable of sinking
current at a compliance up to 2.465V.
BAT2 (Pin 20): This pin is used to connect the battery to
the internal preset voltage setting resistor. An internal
switch disconnects the internal divider from the battery
when the device is in shutdown or when power is disconnected. This disconnect function eliminates the current
drain due to the resistor divider. This pin should be
connected to the positive node of the battery if the internal
preset divider is used. This pin should be grounded if an
external divider is used. Maximum input voltage on this
pin is 20V.
SENSE (Pin 21): This pin is the noninverting input to the
current amplifier CA1 in the Block Diagram. Typical bias
current is – 50µA.
SPIN (Pin 22): This pin is for the internal amplifier CA1
bias. It must be connected as shown in the application
circuit.
BAT (Pin 23): Current Amplifier CA1 Inverting Input.
Typical bias current is – 50µA.
VCC (Pin 24): Input Supply. For good bypass, a low ESR
capacitor of 10µF or higher is required. Keep the lead
length to a minimum. VCC should be between 11V and 24V.
Do not force VCC below VBAT by more than 1V with the
battery present.
BOOSTC (Pin 25): This pin is used to bootstrap and supply
the current sense amplifier CA1 for very low dropout
condition. VCC can be as low as only 0.4V above the battery
voltage. A diode and a capacitor are needed to get the
voltage from VBOOST. If low dropout is not needed and VCC
is always 3V or higher than VBAT, this pin can be left
floating or tied to VCC. Do not force this pin to a voltage
lower than VCC. Typical input current is 1mA.
GBIAS (Pin 26): This is the output of the internal 9.1V
regulator to power the drivers and control circuits. This pin
must be bypassed to a ground plane with a minimum of
2.2µF ceramic capacitor. Switching will stop when VGBIAS
drops below 7V.
BGATE (Pin 27): Low Side Power MOSFET Drive.
PGND (Pin 28): MOSFET Driver Power Ground. A solid
system ground plane is very important. See the LT1505
Demo Manual for further information.
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LT1505
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BLOCK DIAGRAM
(LT1505)
VIN
VCC
8
VCC
INFET
+
VCC
UV
–
7
E8
–
+
7.8V
+
E2
6.7V
+
Q4
A13
VCC
6.7V
SHUTDOWN
E3
+ +
BAT
0.2V
–
VCC 24
E1
A1
50k
3
–
SW
E7
+
–
BGATE
A4
+
A3
+
+
+
–
4U
2.5V
4V
26
+
A6
S
27
A9
R
A7
ONE
SHOT
28
+
–
25
A12
Q2
Q3
22
+
0.02V
+
IVA
4
Q1
21
BGATE
RS1
–
+
12.6V
BATTERY
M2
PGND
BOOSTC
SPIN
SENSE
RS3
BAT
RS2
IPROG
CA1
–
SLOPE COMP
CAP 12
IBAT
VRS1
50k
A10
OSC
200k
VRS1
GBIAS
+
A5
A8
1.3V
L1
10µH
C3
4.7µF
9.1V
E4
+
SYNC 4
SW
E5
+
5
M1
2
–
7V
SHUTDOWN
7V
SHDN
TGATE
A2
–
+
VIN
C2
1µF
+
+
GBIAS
BOOST
1
23
PWM
IPROG
–
–
C1
+
B1
R2
BAT2
A11
+
–
+
20
–
E6
+
FLAG 13
IPROG
R1
1k
+
3.3V
R3
R4
50.55k
16
R5
21k
+
IVA
17
3CELL
VFB
VA
VREF
2.465V
–
–
CA2
+
R8
75k
14 4.1V
R6
0.33k
15
VREF
4.2V
R7
12.3k
VIN
92mV
+
9
CLP
RS
+
CL1*
–
6
AGND
18
19
VC
CPROG
PROG
11
COMP1
10
1505 BD
CLN
VCC
SYSTEM
LOAD
RPROG
*LT1505 ONLY. SEE PIN FUNCTIONS
FOR LT1505-1 CONNECTIONS
1505fc
8
LT1505
TEST CIRCUITS
Test Circuit 1
SPIN
LT1505
+
–
VC
CA1
CA2
1k
+
75k
0.047µF
–
SENSE
RS3
200Ω
BAT
RS2
200Ω
RS1
10Ω
+
VBAT
VREF
PROG
1µF
RPROG
300Ω
+
LT1006
1k
1505 TC01
–
+
≈ 0.65V
20k
Test Circuit 2
LT1505
VFB OR BAT2
+
VA
–
VREF
PROG
IPROG
2k
0.47µF
RPROG
–
+
+
2nF
LT1013
1505 TC02
2.465V
Test Circuit 3
LT1505
+
CAP
IVA
4
0.047µF
–
FLAG
IPROG
E6
2V
1k
+
–
+
+
RS2 VRS1
200Ω
–
10Ω
+
VBAT
+
VFB
VA
–
IVA
LT1013
BAT
IPROG
3.3V
0.033µF
RS3
200Ω
+
CA1
–
+
SENSE
VREF
PROG
20k
10k
–
10k
0.47µF
4.93k
+
LT1013
+
2.465V
1505 TC03
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OPERATION
The LT1505 is a synchronous current mode PWM stepdown (buck) switcher. The battery DC charge current is programmed by a resistor RPROG (or a DAC output current) at
the PROG pin and the ratio of sense resistors RS2 over RS1
(see Block Diagram). Amplifier CA1 converts the charge current through RS1 to a much lower current IPROG (IPROG =
IBAT • RS1/RS2) fed into the PROG pin. Amplifier CA2 compares the output of CA1 with the programmed current and
drives the PWM loop to force them to be equal. High DC
accuracy is achieved with averaging capacitor CPROG. Note
that IPROG has both AC and DC components. IPROG goes
through R1 and generates a ramp signal that is fed to the
PWM control comparator C1 through buffer B1 and level
shift resistors R2 and R3, forming the current mode inner
loop. The BOOST pin supplies the topside power switch gate
drive. The LT1505 generates an 9.1V VGBIAS to power drives
and VBOOSTC. BOOSTC pin supplies the current amplifier
CA1 with a voltage higher than VCC for low dropout application. For batteries like lithium that require both constantcurrent and constant-voltage charging, the 0.5% 2.465V
reference and the amplifier VA reduce the charge current
when battery voltage reaches the preset level. For NiMH and
NiCd, VA can be used for overvoltage protection.
The amplifier CL1 monitors and limits the input current,
normally from the AC adapter, to a preset level (92mV/RS).
At input current limit, CL1 will supply the programming
current IPROG, thus reducing battery charging current.
To prevent current shoot-through between topside and
lowside switches, comparators A3 and A4 assure that one
switch turns off before the other is allowed to turn on.
Comparator A12 monitors charge current level and turns
lowside switch off if it drops below 20% of the programmed
value (20mV across RS1) to allow for inductor discontinuous mode operation. Therefore sometimes even in continuous mode operation with light current level the lowside
switch stays off.
Comparator E6 monitors the charge current and signals
through the FLAG pin when the charger is in voltage mode
and the charge current level is reduced to 20%. This charge
complete signal can be used to start a timer for charge
termination.
The INFET pin drives an external P-channel FET for low
dropout application.
When input voltage is removed, VCC will be held up by the
body diode of the topside MOSFET. The LT1505 goes into
a low current, 10µA typical, sleep mode as VCC drops
below the battery voltage. To shut down the charger
simply pull the VC pin or SHDN pin low with a transistor.
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APPLICATIONS INFORMATION
Input and Output Capacitors
In the 4A Lithium Battery Charger (Figure 1), the input
capacitor (CIN) is assumed to absorb all input switching
ripple current in the converter, so it must have adequate
ripple current rating. Worst-case RMS ripple current will
be equal to one half of output charging current. Actual
capacitance value is not critical. Solid tantalum capacitors
such as the AVX TPS and Sprague 593D series have high
ripple current rating in a relatively small surface mount
package, but caution must be used when tantalum capacitors are used for input bypass. High input surge currents
can be created when the adapter is hot-plugged to the
charger and solid tantalum capacitors have a known
failure mechanism when subjected to very high turn-on
surge currents. Highest possible voltage rating on the
capacitor will minimize problems. Consult the manufacturer before use. Alternatives include new high capacity
ceramic (at least 20µF) from Tokin or United Chemi-Con/
Marcon, et al.
The output capacitor (COUT) is also assumed to absorb
output switching current ripple. The general formula for
capacitor current is:
(
)
V
0.29 (VBAT) 1 – BAT
VCC
IRMS =
(L1)(f)
For example, VCC = 19V, VBAT = 12.6V, L1 = 15µH,
and f = 200kHz, IRMS = 0.4A.
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APPLICATIONS INFORMATION
EMI considerations usually make it desirable to minimize
ripple current in the battery leads. Beads or inductors may
be added to increase battery impedance at the 200kHz
switching frequency. Switching ripple current splits between the battery and the output capacitor depending on
the ESR of the output capacitor and the battery impedance. If the ESR of COUT is 0.2Ω and the battery impedance
is raised to 4Ω with a bead or inductor, only 5% of the
ripple current will flow in the battery.
92mV
+
+
CLP
1µF
CL1
–
CLN
In any switching regulator, conventional timer-based soft
starting can be defeated if the input voltage rises much
slower than the time out period. This happens because the
switching regulators in the battery charger and the computer power supply are typically supplying a fixed amount
of power to the load. If input voltage comes up slowly
compared to the soft start time, the regulators will try to
deliver full power to the load when the input voltage is still
well below its final value. If the adapter is current limited,
it cannot deliver full power at reduced output voltages and
the possibility exists for a quasi “latch” state where the
adapter output stays in a current limited state at reduced
output voltage. For instance, if maximum charger plus
computer load power is 30W, a 15V adapter might be
current limited at 2.5A. If adapter voltage is less than
(30W/2.5A = 12V) when full power is drawn, the adapter
voltage will be pulled down by the constant 30W load until
it reaches a lower stable state where the switching regulators can no longer supply full load. This situation can be
prevented by setting undervoltage lockout higher than the
minimum adapter voltage where full power can be achieved.
RS4*
VCC
AC ADAPTER
OUTPUT
VIN
+
CIN
LT1505
R5
UV
*RS4 =
Soft Start and Undervoltage Lockout
The LT1505 is soft started by the 0.33µF capacitor on the
VC pin. On start-up, the VC pin voltage will rise quickly to
0.5V, then ramp up at a rate set by the internal 45µA pullup current and the external capacitor. Battery charge
current starts ramping up when VC voltage reaches 0.7V
and full current is achieved with VC at 1.1V. With a 0.33µF
capacitor, time to reach full charge current is about 10ms
and it is assumed that input voltage to the charger will
reach full value in less than 10ms. The capacitor can be
increased up to 1µF if longer input start-up times are
needed.
500Ω
92mV
ADAPTER CURRENT LIMIT
R6
1505 F02
Figure 2. Adapter Current Limiting
A resistor divider is used to set the desired VCC lockout
voltage as shown in Figure 2. A typical value for R6 is 5k
and R5 is found from:
R5 =
R6(VIN – VUV )
VUV
VUV = Rising lockout threshold on the UV pin
VIN = Charger input voltage that will sustain full load power
Example: With R6 = 5k, VUV = 6.7V and setting VIN at 16V;
R5 = 5k (16V – 6.7V)/6.7V = 6.9k
The resistor divider should be connected directly to the
adapter output as shown, not to the VCC pin to prevent
battery drain with no adapter voltage. If the UV pin is not
used, connect it to the adapter output (not VCC) and
connect a resistor no greater than 5k to ground. Floating
the pin will cause reverse battery current to increase from
10µA to 200µA.
Adapter Current Limiting
(Not Applicable for the LT1505-1)
An important feature of the LT1505 is the ability to
automatically adjust charge current to a level which avoids
overloading the wall adapter. This allows the product to
operate at the same time batteries are being charged
without complex load management algorithms. Additionally, batteries will automatically be charged at the maximum
possible rate of which the adapter is capable.
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This is accomplished by sensing total adapter output
current and adjusting charge current downward if a preset
adapter current limit is exceeded. True analog control is
used, with closed loop feedback ensuring that adapter load
current remains within limits. Amplifier CL1 in Figure 2
senses the voltage across RS4, connected between the
CLP and CLN pins. When this voltage exceeds 92mV, the
amplifier will override programmed charge current to limit
adapter current to 92mV/RS4. A lowpass filter formed by
500Ω and 1µF is required to eliminate switching noise. If
the current limit is not used, then the R7 /C1 filter and the
COMP1 (R1/C7) compensation networks are not needed,
and both CLP and CLN pins should be connected to VCC.
Charge Current Programming
The basic formula for charge current is (see Block
Diagram):
IBAT = IPROG
( )(
RS2
2.465V
=
RS1
RPROG
)( )
RS2
RS1
where RPROG is the total resistance from PROG pin to ground.
For the sense amplifier CA1 biasing purpose, RS3 should
have the same value as RS2 and SPIN should be connected
directly to the sense resistor (RS1) as shown in the Block
Diagram.
For example, 4A charging current is needed. For low power
dissipation on RS1 and enough signal to drive the amplifier
CA1, let RS1 = 100mV/4A = 0.025Ω. This limits RS1 power
to 0.4W. Let RPROG = 5k, then:
)(R )
(I )(R
RS2 = RS3 = BAT PROG S1
2.465V
(4A)(5k)(0.025)
=
= 200Ω
2.465V
5V
0V
Q1
VN2222
PWM
Note that for charge current accuracy and noise immunity, 100mV full scale level across the sense resistor RS1
is required. Consequently, both RS2 and RS3 should be
200Ω.
It is critical to have a good Kelvin connection on the
current sense resistor RS1 to minimize stray resistive
and inductive pickup. RS1 should have low parasitic
inductance (typical 3nH or less, as exhibited by Dale or
IRC sense resistors). The layout path from RS2 and RS3
to RS1 should be kept away from the fast switching SW
node. Under low charge current conditions, a low quality
sense resistor with high ESL (4nH or higher) coupled
with a very noisy current sense path might false trip
comparator A12 and turn on BGATE at the wrong time,
potentially damaging the bottom power FET. In this case,
an RC filter of 10Ω and 10nF should be used across RS1
to filter out the noise (see Figure 4).
L1
+ VRS1 –
RS1
+
LT1505
SPIN
–
10Ω
BATTERY
RS2
RS3
BAT
10nF
BAT2
1505 F04
Figure 4. Reducing Current Sensing Noise
Lithium-Ion Charging
PROG
IBAT = (DC)(4A)
When a microprocessor DAC output is used to control
charge current, it must be capable of sinking current at a
compliance up to 2.5V if connected directly to the PROG
pin.
SENSE
LT1505
RPROG
4.7k
Charge current can also be programmed by pulse width
modulating IPROG with a switch Q1 to RPROG at a frequency
higher than a few kHz (Figure 3). Charge current will be
proportional to the duty cycle of the switch with full current
at 100% duty cycle.
CPROG
1µF
1505 F03
Figure 3. PWM Current Programming
The 4A Lithium Battery Charger (Figure 1) charges lithiumion batteries at a constant 4A until battery voltage reaches
the preset value. The charger will then automatically go
into a constant-voltage mode with current decreasing to
near zero over time as the battery reaches full charge.
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APPLICATIONS INFORMATION
Preset Battery Voltage Settings
Lithium-Ion Charging Completion
The LT1505 provides four preset battery voltages: 12.3V,
12.6V, 16.4V and 16.8V. See the Pin Functions section for
pin setting voltage selection. An internal switch connects
the resistor dividers to the battery sense pin, BAT2. When
shutting down the LT1505 by removing adaptor power or
by pulling the SHDN pin low, the resistor dividers will be
disconnected and will not drain the battery. The BAT2 pin
should be connected to the battery when any of the preset
battery voltages are used.
Some battery manufacturers recommend termination of
constant-voltage float mode after charge current has
dropped below a specified level (typically around 20% of
the full current) and a further time-out period of 30
minutes to 90 minutes has elapsed. Check with manufacturers for details. The LT1505 provides a signal at the
FLAG pin when charging is in voltage mode and current is
reduced to 20% of full current, assuming full charge
current is programmed to have 100mV across the current
sense resistor (VRS1). The comparator E6 in the Block
Diagram compares the charge current sample IPROG to the
output current IVA voltage amplifier VA. When the charge
current drops to 20% of full current, IPROG will be equal to
0.25 IVA and the open-collector output VFLAG will go low
and can be used to start an external timer. When this
feature is used, a capacitor of at least 0.1µF is required at
the CAP pin to filter out the switching noise and a pull-up
resistor is also needed at the FLAG pin. If this feature is not
used, C6 is not needed.
External Battery Voltage Setting Resistors
When an external divider is used for other battery voltages, BAT2 should be grounded. Pins 4.1V, 4.2V and
3CELL should be left floating. To minimize battery drain
when the charger is off, current through the R3/R4 divider
(Figure 5) is set at 15µA . The input current to the VFB pin
is 3nA and the error can be neglected.
With divider current set at 15µA, R4 = 2.465/15µA = 162k
and,
(R4)(VBAT − 2.465) = 162k (8.4 − 2.465)
R3 =
2.465
2.465
= 390k
LT1505
VFB
R3
390k
0.25%
VBAT
+
8.4V
R4
162k
0.25%
1505 F04
Figure 5. External Resistor Divider
Li-Ion batteries typically require float voltage accuracy of
1% to 2%. Accuracy of the LT1505 VFB voltage is ±0.5%
at 25°C and ±1% over the full temperature range. This
leads to the possibility that very accurate (0.1%) resistors
might be needed for R3 and R4. Actually, the temperature
of the LT1505 will rarely exceed 50°C in float mode
because charging currents have tapered off to a low level,
so 0.25% resistors will normally provide the required level
of overall accuracy.
Very Low Dropout Operation
The LT1505 can charge the battery even when VCC goes
as low as 0.5V above the combined voltages of the
battery and the drops on the sense resistor as well as
parasitic wiring. This low VCC sometimes requires a duty
factor greater then 99% and TGATE stays on for many
switching cycles. While TGATE stays on, the voltage
VBOOST across the capacitor C2 drops down because
TGATE control circuits require 2mA DC current. C2 needs
to be recharged before VBOOST drops too low to keep the
topside switch on. A unique design allows the LT1505 to
operate under these conditions; the comparator A2 monitors VBOOST and when it drops from 9.1V to 6.9V, TGATE
will be turned off for about 0.2µs to recharge C2. Note that
the LT1505 gets started the same way when power turns
on and there is no initial VBOOST.
It is important to use 0.56µF or greater value for C2 to hold
VBOOST up for a sufficient amount of time.
When minimum operating VCC is less than 2.5V above the
battery voltage, D3 and C4 (see Figure 1) are also needed
to bootstrap VBOOSTC higher than VCC to bias the current
1505fc
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LT1505
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APPLICATIONS INFORMATION
amplifier CA1. They are not needed if VCC is at least 2.5V
higher than VBAT. The PFET M3 is optional and can be
replaced with a diode if VIN is at least 3V higher than VBAT.
The gate control pin INFET turns on M3 when VIN gets up
above the undervoltage lockout level set by R5 and R6 and
is clamped internally to 8V below VCC. In sleep mode when
VIN is removed, INFET will clamp M3 VSG to 0.2V.
Nickel-Cadmium and Nickel-Metal-Hydride Charging
The circuit in the 4A Lithium Battery Charger (Figure 1) can
be modified to charge NiCd or NiMH batteries. For
example, 2-level charging is needed; 2A when Q1 is on,
and 200mA when Q1 is off (Figure 8).
24V ≤ VCC < 27V
VIN
Shutdown
3M
LT1505
When adapter power is removed, VCC will drift down and
be held by the body diode of the topside NFET switch. As
soon as VCC goes down to 0.2V above VBAT, the LT1505 will
go into sleep mode drawing only 10µA from the battery.
3.3µF
1505 F05
Figure 6. High Input Voltage Shudown
There are two ways to stop switching: pulling the SHDN
pin low or pulling the VC pin low. Pulling the SHDN pin low
will also turn off VGBIAS and CA1 input currents. Pulling the
VC pin low will only stop switching and VGBIAS stays high.
Make sure there is a pull-up resistor on the SHDN pin even
if the SHDN pin is not used, otherwise internal pull-down
current will keep the SHDN pin low and switching off when
power turns on.
5V TO 20V
5k
Synchronization
The LT1505 can be synchronized to a frequency range
from 240kHz to 280kHz. With a 200ns one-shot timer on
chip, the LT1505 provides flexibility on the synchronizing
pulse width. Sync pulse threshold is about 1.2V (Figure 7).
LT1505
SYNC
VN2222
PULSE WIDTH > 200ns
1505 F06
Figure 7. Synchronizing with External Clock
Each TGATE and BGATE pin has a 50k pull-down resistor
to keep the external power FETs off when shut down or
power is off.
Note that maximum operating VCC is 24V. For short
transients the LT1505 can be operated as high as 27V. For
VCC higher than 24V it is preferred to use the VC pin to shut
down. If the SHDN pin has to be used to shut down at VCC
higher than 24V, the Figure 6 pull-up circuit must be used
to slow down the VGBIAS ramp-up rate when the SHDN pin
is released. Otherwise, high surge current charging the
bypass capacitor might damage the LT1505. For VCC less
than 24V, only a 100k resistor and no capacitor is needed
at SHDN pin to VIN for pull-up.
OPEN DRAIN
SHDN
LT1505
PROG
CPROG
1µF
R2
5.49k
R1
49.3k
Q1
1505 F07
Figure 8. 2-Level Charging
For 2A full current, the current sense resistor (RS1) should
be increased to 0.05Ω so that enough signal (10mV) will
be across RS1 at 0.2A trickle charge to keep charging
current accurate.
For a 2-level charger, R1 and R2 are found from:
R1 =
(2.465)(4000)
ILOW
R2 =
(2.465)(4000 )
IHI − ILOW
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All battery chargers with fast charge rates require some
means to detect full charge state in the battery to terminate
the high charge current. NiCd batteries are typically charged
at high current until temperature rise or battery voltage
decrease is detected as an indication of near full charge.
The charge current is then reduced to a much lower value
and maintained as a constant trickle charge. An intermediate “top off” current may be used for a fixed time period
to reduce 100% charge time.
NiMH batteries are similar in chemistry to NiCd but have
two differences related to charging. First, the inflection
characteristic in battery voltage as full charge is approached is not nearly as pronounced. This makes it
more difficult to use – ∆V as an indicator of full charge,
and an increase in temperature is more often used with a
temperature sensor in the battery pack. Secondly, constant trickle charge may not be recommended.
Instead, a moderate level of current is used on a pulse
basis (≈ 1% to 5% duty cycle) with the time-averaged
value substituting for a constant low trickle. Please
contact the Linear Technology Applications department
about charge termination circuits.
If overvoltage protection is needed, R3 and R4 in Figure 5
should be calculated according to the procedure described
in the Lithium-Ion Charging section. The VFB pin should be
grounded if not used.
Charger Crowbar Protection
If the VIN connector of Figure 1 can be instantaneously
shorted (crowbarred) to ground, then a small P-channel FET
M4 should be used to quickly turn off the input
P-channel FET M3 (see Figure 9), otherwise, high reverse
surge current might damage M3. M3 can also be replaced
by a diode if dropout voltage and heat dissipation are not
problems.
Note that the LT1505 will operate even when VBAT is
grounded. If VBAT of Figure 1 charger gets shorted to
ground very quickly (crowbarred) from a high battery
voltage, slow loop response may allow charge current to
build up and damage the topside N-channel FET M1. A
small diode D5 (see Figure 10) from the SHDN pin to VBAT
will shut down switching and protect the charger.
Note that M4 and/or D5 are needed only if the charger
system can be potentially crowbarred.
RS4
M3
VIN
VCC
M4
TPO610
LT1505
INFET
1505 F08
Figure 9. VIN Crowbar Protection
VIN
100k
LT1505
SHDN
D5
1N4148
VBAT
1505 F09
Figure 10. VBAT Crowbar Protection
Layout Considerations
Switch rise and fall times are under 20ns for maximum
efficiency. To prevent radiation, the power MOSFETs, the
SW pin and input bypass capacitor leads should be kept as
short as possible. A Schottky diode (D4 in Figure 1) rated
for at least 1A is necessary to clamp the SW pin and should
be placed close to the low side MOSFET. A ground plane
should be used under the switching circuitry to prevent
interplane coupling and to act as a thermal spreading path.
Note that the inductor is probably the most heat dissipating device in the charging system. The resistance on a 4A,
15µH inductor, can be 0.03Ω . With DC and AC losses, the
power dissipation can go as high as 0.8W. Expanded
traces should be used for the inductor leads for low
thermal resistance.
The fast switching high current ground path including the
MOSFETs, D4 and input bypass capacitor should be kept
very short. Another smaller input bypass (1µF ceramic)
should be placed very close the chip. The demo board
DC219 should be used for layout reference.
1505fc
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LT1505
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PACKAGE DESCRIPTION
G Package
28-Lead Plastic SSOP (5.3mm)
(Reference LTC DWG # 05-08-1640)
10.07 – 10.33*
(.397 – .407)
28 27 26 25 24 23 22 21 20 19 18 17 16 15
7.65 – 7.90
(.301 – .311)
1 2 3 4 5 6 7 8 9 10 11 12 13 14
5.20 – 5.38**
(.205 – .212)
1.73 – 1.99
(.068 – .078)
0° – 8°
.13 – .22
(.005 – .009)
.65
(.0256)
BSC
.55 – .95
(.022 – .037)
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
2. DIMENSIONS ARE IN
(INCHES)
.25 – .38
(.010 – .015)
.05 – .21
(.002 – .008)
G28 SSOP 0501
3. DRAWING NOT TO SCALE
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED .152mm (.006") PER SIDE
**DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1372/LT1377
1.5A, 500kHz/1MHz Step-Up Switching Regulators
High Frequency, Small Inductor, High Efficiency Switchers, SO-8
LT1376
1.5A, 500kHz Step-Down Switching Regulator
High Frequency, Small Inductor, High Efficiency Switcher, SO-8
LT1510
Constant-Voltage/Constant-Current Battery Charger
Up to 1.5A Charge Current, Small SO-8 Footprint
LT1511
3A Constant-Voltage/Constant-Current Battery Charger
Charges Lithium, NiCd and NiMH Batteries, 28-Lead SO Package
LT1512
SEPIC CC/CV Battery Charger
VIN Can Be Higher or Lower Than Battery Voltage, 2A Internal Switch
LT1513
SEPIC CC/CV Battery Charger
VIN Can Be Higher or Lower Than Battery Voltage, 3A Internal Switch
LT1571
Constant-Voltage/Constant-Current Battery Charger
1.5A Charge Current, Preset Voltage for 1 or 2 Li-Ion Cells, C/10 Flag
LTC1731
Linear Charger Controller
Programmable Timer; 8-Pin MSOP; C/10 Flag
LTC1732
Linear Charger Controller
AC Adapter Present Flag; Programmable Timer; 10-Pin MSOP; C/10 Flag
LTC1733
Linear Charger with Integrated FET
1.5A Charge Current, Programmable Timer,
10-Pin Thermally Enhanced MSOP Package
LTC1734
Linear Charger Controller
Inexpensive Constant-Voltage/Constant-Current Li-Ion Charger,
5-Pin SOT-23 Package
LTC1759
SMBus Controlled Smart Battery Charger
LT1505 Charger Functionality with SMBus Control
LT1769
2A Constant-Voltage/Constant-Current Battery Charger
Charges Lithium, NiCd and NiMH Batteries, 20-Lead Exposed Pad TSSOP
LTC1960
Dual Battery Charger and Selector with SPI Interface
ICHARGE up to 6A, Fast Charge, Longer Battery Life, Crisis Management
1505fc
16
Linear Technology Corporation
LT/TP 1101 1.5K REV C • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
 LINEAR TECHNOLOGY CORPORATION 1999